Q: Since thunder and lightning are electrical events, why are they so often accompanied by heavy rain?
The electrical activity that manifests itself as lightning is generated by the airborne water. The thunder is sound waves resulting from the extreme heat of the lightning.
As the National Oceanic and Atmospheric Administration explains, the ingredients necessary for a thunderstorm are moisture; rising, unstable air; and a lifting mechanism, like hills or mountains or just the collision of masses of warm, wet air and cold, dry air.
When water vapor condenses into a cloud and rises into colder upper regions of the sky, some of it turns into ice crystals, usually with a positive charge, and some becomes water droplets, usually with a negative charge.
When the charges are strong enough, the electricity is discharged as a bolt of lightning. While some lightning often precedes rain, the main event occurs as a downdraft starts and rain or other precipitation falls. Eventually, the downdraft overcomes the updraft and the storm dissipates, along with the lightning.
When peaches get poached
Q: Peaches lose their sweetness when poached, but the water remains bland. Where does the sugar go?
It is not that the sugar is getting out but that the water is getting into the peach cells, said Dr. Gavin Sacks, an assistant professor of food science at Cornell University.
This is an example of osmosis, he said the movement of a solvent (water) across a membrane (the peach cell wall) from an area of low dissolved solids (the poaching liquid) to one of high dissolved solids (inside the peach cells).
The water molecule is smaller than those of sugars, and it passes through cell walls more easily. With salt cod or ham, salt or sugar (or both) is put on the surface; water passes through the cell walls, drying the food. The reverse should happen with poached peaches, since the dissolved-solids content is higher inside them.
Sacks tried poaching a few nectarines in water. On average, the nectarines weighed almost 50 percent more after poaching than before, he said. The sugar content dropped from over 14 percent by weight to close to 10 percent, but the sugar content of the poaching water was 0.5 percent, barely detectable to our tongues. So it looks like dilution due to osmosis is the answer.